The cochleas of new-born guinea pigs are being studied by means of the Golgi, the ACHE and the Maallet stains, and electron microscopy in order to throughly define the details of the cochlear and efferent nerve pattern. Dyeinjection methods are also being employed. The innervation pattern of the avian cochlea will also be studied by means of the Golgi stain. We have already used the Holmes silver stain and the Karnovsky ACHE stain on the pigion's cochlea so that we are familiar with the general patterns of innervation. The Golgi method is necessary for tracing single nerve fibers.